The present invention relates to an insertion coupling for a boring rod assembly as well as to a boring rod assembly having one or several such insertion couplings.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Several methods and devices have been developed for introducing horizontal bore holes in the ground. New pipes or cables for supplying, for example, water or electricity can be inserted simultaneously or at a later time into these bore holes.
Some conventional horizontal boring apparatuses introduce a bore hole in the ground with a boring assembly having a bore head attached to the front end by way of a drive apparatus arranged in a starting shaft or above ground.
A thrust force as well as a torque is transmitted to the bore head by the drive apparatus to advance the bore head in the ground. It is also known to provide this drive apparatus additionally with an impact drive, which can be activated as needed, when the bore head hits in the ground an obstacle, for example a rock. The obstacle is then destroyed by producing impact pulses and transmitting the impact pulses to the bore head via the boring rod assembly, whereafter a normal, i.e., pushing and rotating boring operation can be resumed. In general, the boring rod assemblies used with these horizontal boring apparatuses have sections (rod sections) connected with each other via screw connections. Screwing the individual rod sections together can be performed automatically with a suitable design of the drive apparatus. Advantageously, the use of screw connections with boring rod assemblies for the aforedescribed horizontal boring apparatuses results in relatively low manufacturing costs and the elimination of play in the transmission of both pressing forces (in particular also impact pulses) and pulling forces as well as torque in at least one rotation direction. Disadvantageously, however, (large) torques can fundamentally not be transmitted in the release location direction of the screw connection. In addition, screwing together the individual rod sections is time-consuming even if performed automatically.
Rod assemblies are known in the technical field of trenchless pipe installation, wherein the pipe sections are connected with each other by insertion couplings. These assemblies are pushed from a target shaft (for a pipe to be installed) with a pulling device, which may also be configured to apply a push, through an already established bore or a channel pipe to be restored and are connected to with the pipe to be installed via an adapter after reaching a starting shaft. The pipe is then pulled into the bore or channel pipe with the pulling apparatus. Such assemblies must be able to transmit large pulling forces, but only small pressing forces (during the initial push from the target shaft into the starting shaft) and no impact pulses or torques at all. For this reason, no boring rod assemblies connected with each other by insertion couplings have been used to date for the aforedescribed horizontal boring apparatuses, where the boring assembly is driven through the ground by an aboveground drive unit by both pushing as well as rotating and partially by performing impact pulses.
It would therefore be desirable and advantageous to address this problem and to obviate other prior art shortcomings by providing a boring rod assembly with a plurality of rod sections, wherein the rod sections can be easily connected with each other and are able to reliably transmit even large pressing forces.